RF sensor heat shield

Abstract

A radio-frequency (RF) heat shield for electronics includes a first and second outer skin formed of an insulating material, an insulating core layer arranged between the first and second outer skin, wherein the insulating core layer has a lower dielectric constant as compared with a higher dielectric constant of the first and second outer skin, and a frequency selective surface (FSS) layer including a reflective metallization pattern that is RF transparent and formed on an exterior surface of each of the first and second outer skin.

What is claimed is: 
     
       1. A radio-frequency (RF) heat shield for electronics, the RF heat shield being arranged within an exterior radome between the exterior radome and the electronics, the RF heat shield comprising:
 a first and second outer skin formed of an insulating material; 
 an insulating core layer arranged between the first and second outer skin, wherein the insulating core layer has a lower dielectric constant as compared with a higher dielectric constant of the first and second outer skin; and a frequency selective surface (FSS) layer including a reflective metallization pattern that is RF transparent at a predetermined frequency range and formed on an outermost surface of each of the first and second outer skin, the RF heat shield being configured for forward RF transmission and for thermally insulating the electronics from radiation heat transfer from the exterior radome. 
 
     
     
       2. The RF heat shield according to  claim 1 , wherein the higher dielectric constant is between 3.0 and 4.5, the lower dielectric constant is 1.4 or less, and a loss tangent of both the first and second outer skin and the insulating core layer is 0.005 or less. 
     
     
       3. The RF heat shield according to  claim 1 , wherein the insulating material is quartz. 
     
     
       4. The RF heat shield according to  claim 1 , wherein the FSS layer is formed of a pure metal material that is gold, silver, or copper. 
     
     
       5. The RF heat shield according to  claim 1 , wherein the FSS layer has a thickness that is between 0.02 and 0.2 microns. 
     
     
       6. The RF heat shield according to  claim 1 , wherein the reflective metallization pattern has a plurality of spaced open regions and is formed to cover between 75% and 95% of the outermost surface of each of the first and second outer skin. 
     
     
       7. The RF heat shield according to  claim 1 , wherein the insulating core layer is formed of a fibrous ceramic material. 
     
     
       8. The RF heat shield according to  claim 1 , wherein the first and second outer skin and the insulating core layer are laminated to each other. 
     
     
       9. The RF heat shield according to  claim 1 , wherein the insulating core layer is formed by a vacuum canister, wherein the vacuum canister contains a vacuum or air. 
     
     
       10. The RF heat shield according to  claim 1  further comprising side wall rings or stand-off posts that extend along the insulating core layer between the first and second outer skin, wherein the side wall rings or stand-off posts are formed of another insulating material. 
     
     
       11. The RF heat shield according to  claim 10 , wherein the side wall rings or the stand-off posts and the first and second outer skin are formed of quartz. 
     
     
       12. The RF heat shield according to  claim 10  further comprising bond joints that are formed of a ceramic-based adhesive between the side wall rings and the first and second outer skin. 
     
     
       13. The RF heat shield according to  claim 10  further comprising bond joints that are formed of a fused connection between the side wall rings and the first and second outer skin, whereby a vacuum enclosure is formed to define the core insulating layer. 
     
     
       14. The RF heat shield according to  claim 10  further comprising an inner skin formed of the insulating material of the first and second outer skin, and wherein the insulating core layer is formed of a first insulating core sublayer arranged between the first outer skin and the inner skin and a second insulating core sublayer arranged between the inner skin and the second outer skin. 
     
     
       15. A radome structure comprising:
 an exterior radome; 
 an RF antenna and corresponding sensor electronics arranged in the external radome; and 
 an RF heat shield arranged between the exterior radome and the RF antenna and corresponding sensor electronics, the RF heat shield comprising:
 a first and second outer skin formed of an insulating material; 
 an insulating core layer arranged between the first and second outer skin, wherein the first and second outer skin have a higher dielectric constant that is between 3.0 and 4.5, the insulating core layer has a lower dielectric constant that is 1.4 or less, and a loss tangent of both the first and second outer skin and the insulating core layer is 0.005 or less; and 
 a frequency selective surface (FSS) layer including a reflective metallization pattern that is RF transparent and formed on an outermost surface of each of the first and second outer skin, the RF heat shield being configured for forward RF transmission and for thermally insulating the electronics from radiation heat transfer from the exterior radome. 
 
 
     
     
       16. The radome structure according to  claim 15 , wherein the FSS layer is formed of a pure metal that is gold, silver, or copper, and wherein the reflective metallization pattern has a plurality of spaced open regions and is formed to cover between 75% and 90% of each of the exterior surface of the first and second outer skin. 
     
     
       17. The radome structure according to  claim 15 , wherein the RF heat shield includes side wall rings or stand-off posts that are formed of another insulating material and extend along the insulating core layer between the first and second outer skin. 
     
     
       18. The radome structure according to  claim 15 , wherein the insulating core layer is formed as an enclosed vacuum chamber. 
     
     
       19. A method of forming an RF heat shield for electronics, the RF heat shield being configured to be arranged within an exterior radome between the exterior radome and the electronics, the method comprising:
 selecting an insulating material for outer skins that have a dielectric constant between 3.0 and 4.5 and a loss tangent that is 0.002 or less; 
 selecting another insulating material for an insulating core layer that has a lower dielectric constant than the dielectric constant of the outer skins and a loss tangent that is 0.005 or less; 
 selecting thicknesses of the outer skins and the insulating core layer to obtain a predetermined frequency range; 
 applying a reflective FSS metallization pattern that is RF transparent at a predetermined frequency range on an outermost surface of each of the outer skins using lithography and metal deposition; and 
 sandwiching the insulating core layer between the outer skins, the RF heat shield being configured for forward RF transmission and for thermally insulating the electronics from radiation heat transfer from the exterior radome. 
 
     
     
       20. The method according to  claim 19  further comprising fusing the outer skins to insulating side wall rings of a container defining the insulating core layer thereby forming a vacuum in the insulating core layer.